@Justin *******
as Ellie pointed out NO ONE can apply for an eVisa in Japan not even Japanese nationals because they're not ON the eVisa system yet ๐
you go to the website of the consulate you want to apply at, you read the requirements, meet the requirements, go to the consulate and apply for the visa, wait the processing time and get the visa issued.
here's a screen shot showing japanese national wanting to apply for a thai visa in japan, you see it gets the same error message as you did, so it's nothing to do with your nationality ๐